The present invention relates in general to an endotracheal tube. More particularly, the present invention is concerned with an improved construction of an endotracheal tube for lessening the likelihood of tissue damage and infection in the area of the larynx and trachea. The endotracheal tube of this invention may be adapted for use either by adults or even a newborn.
Usually, persons including tiny infants are intubated with thin-walled round endotracheal tubes which may pass either through the nose or the mouth. Intubation can usually be tolerated for only a relatively short period of time and if the intubation exceeds say 72 hours there may be significant tissue damage to the larynx. In infants this tolerable time period may be somewhat longer but eventually damage will occur.
It is known that the endotracheal tube rests in the posterior commissure of the glottis. The continuous pressure and tube movement due to positive end expiratory pressure and head motion causes changes to occur in the tissue of this area. It has been found that ulceration and erosion of the medial surface of the arytenoid occurs. There also may be thickening and granulation tissue formation of the interarytenoid region. Following ulceration, granulation tissue and scarring or adhesions may occur to interfere with the normal speech or breathing of a person. Furthermore, laryngeal stenosis is a severe medical complication.
Studies have been made with children to determine the effect of intubation. They have found that there is a residual grooving defect of the vocal process, leaving an incomplete glottic closure. The children were asphonic or severely hoarse when the tube was removed.
It has been found that there are possibly a number of reasons for the laryngeal damage. The usual tube that is used is referred to as a Magill tube design having a gradual curving shape. This type of tube results in significant pressure on posterior commissure from the weight of the tongue resting on the tube. Also in the supine patient neck flexion increases the posterior coiling of the tube against the posterior glottis, while the stiffness of the tube wall makes it less likely to bend and conform to the natural curves of the hypopharynx and larynx which is a further source of pressure. Damage is also believed to occur because the tube is round, and yet the posterior commissure and arytenoid areas form a triangular space. This results in damage, especially to the vocal processes of the arytenoids in the midline of a posterior commissure.
Although a tube which is small enough to pass easily through the glottis decreased the pressure, positive pressure ventilation is more effective if a fairly tight seal is created at the glottis. However, if a larger tube is used there is then an increased possibility of irritation and ulceration.
Accordingly, one object of the present invention is to provide an improved construction for an endotracheal tube.
Another object of the present invention is to provide an endotracheal tube that is constructed to reduce or eliminate ulcerations of the larynx.
A further object of the present invention is to provide an endotracheal tube that has a modified cross-sectional shape to more easily conform to the larynx.
Still a further object of the present invention is to provide an endotracheal tube having a cuff disposed at the distal end of the tube and including means for expanding the cuff after the tube has been inserted in the patient.
Still another object of the present invention is to provide an endotracheal tube having an S-shaped configuration.